carburator pop

[pgargus]

have question about new engine just built.when you rev it up sometimes it will pop back threw carburator, have already checked all that i know. has a quadrajet on it. motor is stock

[sunset68]

A backfire through the carb is often an indicator of a lean condition. Maybe the carb is leaning out when you drop the hammer. What RPM does it backfire at? Does it do it consistently?

[thedude327]

Has the carb been sitting awhile? If the power piston is stuck in the down position, you'll get the lean pop. To check if stuck, get a small flashlight and a long flat blade screwdriver and insert it down the vent tube at the front of the carb. gently try to push down on the power piston arm assembly. If it doesn't move, remove the airhorn and gently pry it up and out of the bore it sits in. Then just polish it with some crocus cloth, and reinsert it making sure it isn't sticking. Should do the trick.

Paul